No shell utilizando comando git:
$ export LAST_COMMIT=$(git rev-parse HEAD)
$ echo ${LAST_COMMIT}
132a333e8b798c6a6b7defaad21b47ee3ce7a3aa
Em Python puro com o módulo GitPython:
>>> import git
>>> repo = git.Repo(".")
>>> last_commit = str(repo.head.commit)
>>> print last_commit
132a333e8b798c6a6b7defaad21b47ee3ce7a3aa